How to clone Ubuntu OS partition?

I'm using Macbook Pro 13-inch Late 2011 running Ubuntu 20.04. I used the built-in application called Disks to backup the Ubuntu system partition into a disk image (*.img file) and then restore the disk image back to the partition.

IMPORTANT 

• When backing up a system partition, the EFI system partition should also be backed up if it exists (using either Disks application or cp command)
• The backed up or source partition must be smaller than or equal to the destination partition
• The size of the disk image (*.img file) equals the size of the (backed up) source partition even if the partition has free space. The source partition should be resized as small as possible so that the resulting disk image is acceptably small.

To Backup

Backing up Ubuntu partition:

• Boot into Ubuntu Live (on USB) and chose Try Ubuntu

• Open Disks application from the menu (press Windows key and type Disks)

• Select the partition to backup 

• (Optional) Click on the settings icon for more options and select Resize

• Click on the settings icon for more options then select Create Partition Image...

• Make sure the file name and location are correct. The partition for storing the disk image must be mounted or it'll fail with a message like there is not enough space or something else confusing.

Backing up EFI system partition:

The EFI system partition is where the Ubuntu bootloader locates in because I manually chose the partition for the bootloader while installing Ubuntu (It's a must to install Ubuntu using EFI mode).

I used the method above to clone (backup) this partition, and also manually copied its content using cp command. Of course, using cp command is simpler and works just fine. The partition has only one directory named EFI.

> sudo mkdir /mnt/sda1
> sudo mount -o loop /dev/sda1 /mnt/sda1
> sudo cp -rf /mnt/sda1/EFI /media/myusb/ubuntu-efi/

To Restore

Restoring Ubuntu partition:

• Boot into Ubuntu Live (on USB) and click Try Ubuntu

• Open Disks application from the menu

• Select the (destination) partition for running Ubuntu 

• Click on the settings icon for more options and select Restore Partition Image...

• Browse to the (source) partition that the disk image (*.img file) is stored on

• Select the disk image file and click Start Restoring

Restoring EFI system partition:

I opened Terminal and used the cp command to copy it back from the USB drive to the EFI system partition (in my case, /dev/sda1). 

> sudo mkdir /mnt/sda1     

> sudo mount -o loop /dev/sda1 /mnt/sda1    

> sudo cp -rf /media/myusb/ubuntu-efi/EFI/ubuntu /mnt/sda1/EFI/

> sudo cp -rf /media/myusb/ubuntu-efi/EFI/BOOT /mnt/sda1/EFI/

Successfully Tested Scenarios

Scenario 1 

1. Create a virtual machine and install Ubuntu with VirtualBox, enabling EFI mode
- Partition 1: 500 MB (EFI system)
- Partition 2: 50 GB (FAT32 - empty)
- Partition 3: 200 GB (NTFS - empty)
- Partition 4: 40 GB (EXT4 - Ubuntu)
2. Reboot into Ubuntu Live through a virtual CD-ROM attached with the Ubuntu installation ISO file and choose Try Ubuntu
3. Open Disks application from the menu and use it to backup Partition 4 (Ubuntu system partition) to a disk image (*.img file) stored on Partition 3.
4. Restore the disk image file to Partition 2
5. Format and erase Partition 4
6. Optional: backup Partition 1 to a disk image stored on Partition 3
7. Close the virtual machine and start it again

Scenario 2

1. Boot into Recovery mode on MacBook Pro Late 2011
2. Create the following partitions:
- Partition 1: 70 GB (Mac OS Extended)
- Partition 2: 100 GB (exFAT)
- Partition 3: 90 GB (FAT 32)
- Partition 4: 200 GB (exFAT)
3. Install macOS High Sierra on Partition 1 
4. Install Ubuntu 20.04 on Partition 3 (formatted as ext4)
5. Boot into Ubuntu Live USB and choose Try Ubuntu
6. Open Disks application from the menu
7. Format Partition 4 as NTFS
8. Optional: resize Partition 3 to 20 GB (leaving 70 GB of free space)
9. Backup Partition 3 (Ubuntu) as a disk image (*.img file) and store it on Partition 4 
10. Format and erase Partition 3 (this can also be done in macOS)
11. Restore the disk image from Partition 4 to Partition 3
12. Reboot the machine

Cloning a macOS Big Sur partition to a USB Drive (bootable)

I'm using MacBook Air 2013 running macOS Big Sur. This is how I made a bootable backup of my macOS partition to another partition on my USB drive. Apple Software Restore (asr command line utility) allows a user to restore the content of a (system) volume (disk/partition) to another volume or disk image. This can be thought of cloning a partition.

Step 1

My USB drive has 4 partitions as shown in the image below. The internal system volume (source), macOS Big Sur, is going to be restored to NAK-macOSBigSur partition (target) on the USB drive. The partition is formatted as APFS with GUID Partition Map scheme.

NOTE: This post is about restoring from a snapshot of the system volume (which is explained in the next steps). If there is no snapshot and so it won't be specified in the command, the size of target volume (or disk image) must be greater than the size of the source system volume (not just the size of the system volume's content) or the restore will fail. Just make sure the target volume's size is bigger before the restore and then shrink it later.

Step 2

Note down the identifiers of the source system volume, macOS Big Sur, and the target USB's partition. They can be viewed in DiskUtility or from Terminal using this command:

> diskutil apfs list

APFS Containers (2 found)

|

+-- Container disk1 0A4D95E1-BDA4-4BEF-B349-D34D0B1EAD0B

|   ====================================================

|   APFS Container Reference:     disk1

|   Size (Capacity Ceiling):      89999998976 B (90.0 GB)

|   Capacity In Use By Volumes:   65204166656 B (65.2 GB) (72.4% used)

|   Capacity Not Allocated:       24795832320 B (24.8 GB) (27.6% free)

|   |

|   +-< Physical Store disk0s2 E0056EF5-6FCD-4D45-AB00-C7D273999AE5

|   |   -----------------------------------------------------------

|   |   APFS Physical Store Disk:   disk0s2

|   |   Size:                       89999998976 B (90.0 GB)

|   |

|   +-> Volume disk1s1 23C04205-6361-398C-989F-10195CDC66BA

|   |   ---------------------------------------------------

|   |   APFS Volume Disk (Role):   disk1s1 (Data)

|   |   Name:                      macOS Big Sur - Data (Case-insensitive)

|   |   Mount Point:               /System/Volumes/Data

|   |   Capacity Consumed:         47762022400 B (47.8 GB)

|   |   Sealed:                    No

|   |   FileVault:                 No

|   |

|   +-> Volume disk1s2 0300C5AA-7F28-4FB1-9B21-F128B56BD685

|   |   ---------------------------------------------------

|   |   APFS Volume Disk (Role):   disk1s2 (Preboot)

|   |   Name:                      Preboot (Case-insensitive)

|   |   Mount Point:               /System/Volumes/Preboot

|   |   Capacity Consumed:         284585984 B (284.6 MB)

|   |   Sealed:                    No

|   |   FileVault:                 No

|   |

|   +-> Volume disk1s3 FF1FA02B-5C9E-41E9-8193-4676E5DC57D3

|   |   ---------------------------------------------------

|   |   APFS Volume Disk (Role):   disk1s3 (Recovery)

|   |   Name:                      Recovery (Case-insensitive)

|   |   Mount Point:               Not Mounted

|   |   Capacity Consumed:         623341568 B (623.3 MB)

|   |   Sealed:                    No

|   |   FileVault:                 No

|   |

|   +-> Volume disk1s4 A0B8A157-01F7-4563-9C6A-CC869FE11FB5

|   |   ---------------------------------------------------

|   |   APFS Volume Disk (Role):   disk1s4 (VM)

|   |   Name:                      VM (Case-insensitive)

|   |   Mount Point:               /System/Volumes/VM

|   |   Capacity Consumed:         1074819072 B (1.1 GB)

|   |   Sealed:                    No

|   |   FileVault:                 No

|   |

|   +-> Volume disk1s5 8C1ADEAE-7361-415F-AEBF-C64BD1C00146

|       ---------------------------------------------------

|       APFS Volume Disk (Role):   disk1s5 (System)

|       Name:                      macOS Big Sur (Case-insensitive)

|       Mount Point:               Not Mounted

|       Capacity Consumed:         15330869248 B (15.3 GB)

|       Sealed:                    Broken

|       FileVault:                 No

|       |

|       Snapshot:                  9942DBA2-5C5C-4A6C-B099-79AE2C7B011D

|       Snapshot Disk:             disk1s5s1

|       Snapshot Mount Point:      /

|       Snapshot Sealed:           Yes

|

+-- Container disk3 FD345835-64FB-4924-962B-FB26C2B8F980

    ====================================================

    APFS Container Reference:     disk3

    Size (Capacity Ceiling):      76559953920 B (76.6 GB)

    Capacity In Use By Volumes:   122478592 B (122.5 MB) (0.2% used)

    Capacity Not Allocated:       76437475328 B (76.4 GB) (99.8% free)

    |

    +-< Physical Store disk4s5 17F2CE1B-2E10-411D-8ECF-0435F949DFAE

    |   -----------------------------------------------------------

    |   APFS Physical Store Disk:   disk4s5

    |   Size:                       76559953920 B (76.6 GB)

    |

    +-> Volume disk3s1 714E92A0-4F22-47A0-A72C-449E389BFC23

        ---------------------------------------------------

        APFS Volume Disk (Role):   disk3s1 (No specific role)

        Name:                      NAK-macOSBigSur (Case-insensitive)

        Mount Point:               /Volumes/NAK-macOSBigSur

        Capacity Consumed:         827392 B (827.4 KB)

        Sealed:                    No

        FileVault:                 No

Step  3

Run Apple Software Restore command as following:

> sudo asr restore --source /dev/disk1 --toSnapshot 9942DBA2-5C5C-4A6C-B099-79AE2C7B011D --target /dev/disk5 --erase --buffersize 32m  

Password:

Validating target...done

Validating source...done

Erase contents of /dev/disk5 ()? [ny]: y

Replicating ....10....20....30....40....50....60....70....80....90....100

Replicating ....10....20....30....40....50....60....70....80....90....100

Restored target device is /dev/disk5s2.

Restore completed successfully.

Apple does not allow restoring a system volume when its seal is broken and so is mine, then specifying the --snapshot option is a workaround to bypass the restriction. The snapshot was created by macOS Big Sur automatically when it updated itself and so it's the OS update snapshot.

The seal is part of Signed System Volume (SSV) technology, which is used to protect a system content on a signed system volume. With SSV, the kernel rejects any data or code (at runtime) that does not have a valid cryptographic signature from Apple to protect the integrity of the system content. I'm not sure if the seal is broken because I once booted into Recovery mode and used DiskUtility to restore the system volume to a USB drive. But, some people on the internet said the seal was broken even for a fresh install of Big Sur. 

/dev/disk1 is the identifier of the (source) system volume's container. The identifier of the system volume can also be used, /dev/disk1s1, in this case.

/dev/disk5 is the identifier of the target USB partition's container. The identifier of the partition can also be used, /dev/disk3s1, in this case.

--buffersize 32m option (32m means 32 Megabytes) makes the asr command run faster than the default buffer size. This is ideal for block-copies between partitions.  The size should be changed and experimented for an optimal value.

And the image below shows how my USB drive's partition changed after restore completed.

macOS Sierra

The asr restore command might throw the error below.

Source volume is read-write and cannot be unmounted, so it can't be block copied.

To solve that, the asr restore command must be run in Mac's Recovery mode (restart the machine and hold Command + R).

macOS High Sierra

The asr restore command always fail at the end. Many people reported the same so I downgraded to macOS Sierra.

Errors restoring or creating a disk image from a volume using DiskUtility

I'm using Macbook Air running macOS Big Sur, and I was having troubles performing disk restore using DiskUtility.

ERROR 1: I was unable to restore a volume to a new blank disk image I created. 

There could be a couple reasons such as the size of the blank disk image is smaller than the size of the source volume or there was no partition in the disk image (must be manually created at least 1 partition). But, even if I did follow all these requirements, the restore still failed.

ERROR 2: When trying to create a new disk image from a device or folder, I got the error message like "...operation not permitted". 

The function to create a new image from a device/folder is useful because the size of the new disk image will automatically be set to the size of the source device/folder, and the contents of the device/folder are restored (cloned) to the new disk image. 

SOLUTION

The errors occured because DiskUtility did not have enough privileges to perform those operations. After assigning a Full Disk Access permission to DiskUtility, I could restore a volume to a disk image (and vice versa) without any problems.

How to assign Full Disk Access permission to DiskUtility?

Open System Preferences > Security & Privacy > Privacy then select Full Disk Access from the listbox on the left and click on the Plus sign to add DiskUtility to the right listbox and make sure it's checked.

Backing up macOS with Time Machine

I installed macOS Big Sur on my MacBook Air (11-inch 2013) and used Time Machine application to backup the macOS partition to an external USB drive. 

I also created a bootable macOS Big Sur installation USB stick for restoring the changes back in time using Time Machine, or just installing a fresh macOS Big Sur. In fact, I can also boot into Recovery Mode to perform restore or install too (pressing Command + R while the machine is starting). If the hidden Recovery partition that macOS created is also corrupted or erased, the built-in internet Recovery Mode is used instead. The internet Recovery needs WiFi access to download recovery system image from Apple then start the Recovery mode.

Time Machine backs up the neccesary files to an external hard drive and then uses the backup drive to restore the files back in time. Time Machine can be thought of System Restore in Windows (it's not cloning). I formatted the backup drive using Mac OS Extended (journaled) file system but macOS Big Sur's Time Machine reformatted it as APFS (Case-sensitive). 

Backing up with Time Machine

1. Open System Preferences > Time Machine

2. Click on Select Disk... button and choose a drive or a partition to store the backup files. In my case, the partition's name is Time Machine's Backups (MBA-BigSur) as shown in the image below.

3. Click Options... button and make sure to add any drives or paritions other than the one running OS in the exlusion list

4. Uncheck Backup Automatically so it only backs up when neended.

5. Check Show Time Machine in menu bar then the clock icon will appear at the top of the screen

6. Click on the Time Machine icon in the menu bar and select Back Up Now